Crystal Phase- and Orientation-Dependent Electrical Transport Properties of InAs Nanowires

We report a systematic study on the correlation of the electrical transport properties with the crystal phase and orientation of single-crystal InAs nanowires (NWs) grown by molecular-beam epitaxy. A new method is developed to allow the same InAs NW to be used for both the electrical measurements and transmission electron microscopy characterization. We find both the crystal phase, wurtzite (WZ) or zinc-blende (ZB), and the orientation of the InAs NWs remarkably affect the electronic properties of the field-effect transistors based on these NWs, such as the threshold voltage (V-T), ON-OFF ratio, subthreshold swing (SS) and effective barrier height at the off-state (Phi(OFF)). The SS increases while V-T, ON-OFF ratio, and Phi(OFF) decrease one by one in the sequence of WZ < 0001 >, ZB < 131 >, ZB < 332 >, ZB < 121 >, and ZB < 011 >. The WZ InAs NWs have obvious smaller field-effect mobility, conductivities, and electron concentration at V-BG = 0 V than the ZB InAs NWs, while these parameters are not sensitive to the orientation of the ZB InAs NWs. We also find the diameter ranging from 12 to 33 nm shows much less effect than the crystal phase and orientation on the electrical transport properties of the InAs NWs. The good ohmic contact between InAs NWs and metal remains regardless of the variation of the crystal phase and orientation through temperature-dependent measurements. Our work deepens the understanding of the structure-dependent electrical transport properties of InAs NWs and provides a potential way to tailor the device properties by controlling the crystal phase and orientation of the NWs.